Thursday, November 26, 2015

Is Constraining Global Warming to 2 °C a Fantasy?

Countries have pledged to limit global warming to 2 °C, and climate models say that is still possible. But only with heroic — and unlikely — efforts.

The year is 2100 and the world looks nothing like it did when global leaders gathered for the historic climate summit in Paris at the end of 2015. Nearly 8.8 billion people now crowd the planet. Energy consumption has nearly doubled, and economic production has increased more than sevenfold. Vast disparities in wealth remain, but governments have achieved one crucial goal: limiting global warming to 2 °C above pre-industrial temperatures.

The United Nations meeting in Paris proved to be a turning point. After forging a climate treaty, governments immediately moved to halt tropical deforestation and to expand forests around the globe. By 2020, plants and soils were stockpiling more than 17 billion tonnes of extra carbon dioxide each year, offsetting 50% of global CO2 emissions. Several million wind turbines were installed, and thousands of nuclear power plants were built. The solar industry ballooned, overtaking coal as a source of energy in the waning years of the twenty-first century.

But it took more than this. Governments had to drive emissions into negative terri­tory — essentially sucking greenhouse gases from the skies — by vastly increasing the use of bioenergy, capturing the CO2 generated and then pumping it underground on truly massive scales. These efforts pulled Earth back from the brink. Atmospheric CO2 concentrations peaked in 2060, below the target of 450 parts per million (p.p.m.) and continue to fall.

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That scenario for conquering global warming is one possible — if optimistic — vision of the future.